<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        var str = '100px';
        var num = parseInt(str)
        console.log('num: ', num);
        var num2 = num + 1;
        console.log('num2: ', num2);
        var str2 = num2 + 'px'
        console.log('str2: ', str2);
    </script>
</body>
</html>